The present invention relates to agricultural harvesters and, more particularly, to axial flow combine harvesters having a threshing and separating unit with at least one generally longitudinally arranged rotor for advancing crop material along a generally helical path.
In conventional combine harvesters crop material is fed between a threshing cylinder and an associated threshing concave, which extend transversely to the direction of combine travel. Hereby the crop is threshed over a comparatively short distance. Axial flow machines use one or more longitudinally arranged rotors and associated concaves. Herein, crop material is subjected to a much longer threshing and separating action than in a conventional machine and therefore, the efficiency of axial flow machines is greater because a higher degree of separation is reached and the grain losses are reduced. Commonly, axial flow combines are popular in regions with a continental climate, where the crops to be harvested ripen well and contain hardly any green parts at the time of the harvest. However, when the crop contains green material, such unit is particularly prone to plugging by slugs of accumulated crop material between the rotor and the concaves.
Various means have been provided onto the rotor to optimise the crop flow along the rear portion of the threshing and separating unit and to improve the Orotor performance under adverse conditions. U.S. Pat. No. 4,936,810, for example, suggests to use thinning elements in the form of generally radially extending fingers to smoothen the layer of crop material which is advancing along the concaves. The fingers co-operate with conventional longitudinal bars on the rotor body to move the crop layer along a helical path and to loosen the same. This system is still optimal when harvesting dry crops, but too often slugs occur when handling greener material.
U.S. Pat. No. 5,376,047 discloses a rotor equipped with a multitude of rectangular blades which can be distributed along the surface of the rotor in order to optimize the crop flow. For a particular crop and a particular crop condition, a blade distribution may be found which is optimal with respect to threshing and separating efficiency and/or plugging risks, but such investigation is not within reach of the ordinary operator.
In U.S. Pat. No. 4,178,943 a rotor is shown equipped with generally transverse fins behind the threshing section. The separation capacity of this embodiment is limited because of the restrained action of the fin heads on the layer of crop material. The grain losses at the end of the separation section may raise to unacceptable levels, unless the rate of incoming material is reduced by lowering the ground speed of the combine harvester.
Accordingly there is a need for an effective threshing and separating arrangement which on the one hand has a good separation capacity and on the other hand is not prone to slugs or roping.
According to the present invention, there is provided a combine harvester comprising:
a main frame;
a threshing and separating arrangement mounted to said main frame and including:
a generally cylindrical chamber having a generally longitudinal axis and comprising a separating concave assembly; and
a rotor assembly mounted for rotation in said chamber and comprising a generally cylindrical rotor body with a separating section associated with said separating concave assembly; and
said separating section of said rotor assembly comprising a plurality of longitudinal elements having a leading, generally longitudinally arranged crop engaging face;
characterised in that said separating section further is provided with a plurality of transverse elements having a generally transversely arranged crop engaging edge.
These transverse elements assist in controlling the distribution of straw and other crop material during their passage through the separating section.
The transverse elements may have a leading portion or edge adjacent the rear end of the leading face of one of the longitudinal elements. Their trailing portion may end adjacent a leading face of the next longitudinal element. In this manner the transverse elements bridge the space between the longitudinal elements. The transverse and the longitudinal elements preferably are arranged in an axially staggered pattern.
In order to extend the lifetime of the rotor itself the crop engaging elements may be provided with wear plates which are attached to longitudinal and transverse supports which are affixed to the rotor body.
In order to improve the smoothness of the crop flow, the longitudinal elements may have an outwardly (from the rotor body) and rearwardly (in the direction of the chamber outlet) inclined front edge and/or a leading face which is inclined backwards with respect to the normal rotation of the rotor.
The transverse elements may have a leading edge which is inclined backwards, thereby matching the leading face of the longitudinal elements.
The transverse wear plates may be profiled to present a leading portion extending above its middle portion. The leading portion thereby forms a finger which assists in splitting the crop flow along the concaves.
For enhanced versatility of the separating section, the rotor body may be provided with mounts for generally radially extending thinning rods. In this manner the threshing and separating assembly may be adapted to a wider range of crop and field conditions.
Advantageously the threshing and separating arrangement may comprise a beater assembly arranged behind said concave assembly for receiving threshed and separated crop material therefrom and projecting it rearwardly, said beater assembly comprising a transverse guide means mounted behind said separating concave and below said rotor, and a transverse beater rotor. The threshing chamber may comprise a curved guide plate arranged behind said separating concave and above said guide means for distributing the separated crop material over the full width of said guide means.